<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var arr = ['周一', '周二', '周三', '周四']

    for(var i = 0; i < arr.length; i++) {
      console.log(arr[i])
    }

    // length 长度
    console.log( arr.length )
  </script>
</body>
</html>